HOLMES.] JUNCTION VALLEY. 43 



che most striking topographical features of tlie valley and vicinity are 

 the broad, drilt-covered meadows, lying between Elk Creek and the 

 base of Specimen Eidge, Junction Butte, the well-known landmark of 

 •e valley, and Garnet Hill, which lies at the lower end of the valley. 

 Garnet Hill consists of a heavy angular mass of dark schistose rocks 

 lat have their direct continuation in corresponding strata north of the 

 ver. From all surrounding points and from many points on the trail 

 s steep rugged walls catch the eye. The summit is covered with 

 :unted pines. On the east the dip of the strata gives a rather gentle 

 incline toward the meadows and river. Close under the southwest face 

 is the little stream known as Elk Creek, and the Yellowstone rushes 

 with great force through a ragged canon at the north base. The 

 rocks consist of alternating mica schists and coarse-grained granitic 

 seams. The bedding is quite irregular and there is considerable con- 

 tortion, as if the strata had undergone great pressure. Garnets occur 

 in the greatest quantity and can be seen dotting the faces of the exposed 

 rocks or may be picked up where they are weathered out and mixed 

 with the soil. All are very much flawed and so filled with impurities 

 that they can never have any particular value. Lying against the east- 

 ern and southern flanks of Garnet Hill are the outcropping edges of a 

 sheet of x^eculiarly brecciated trachyte (Nos. 1, 2, and 3, of Captain 

 Button's catalogue) which presents a variety of colors, running through 

 all grades of red, purple, orange, and even green. It rests directly 

 upon the schist and is apparently the oldest of the volcanic products of 

 this district. At various points in the valley of Elk Creek there are 

 outcrops of this rock. It is first encountered on the trail in approaching 

 IVom the Mammoth Springs, shortly after descending the steep Tertiary 

 wall that borders Elk Creek on the west. This is at an elevation of 

 some 500 feet above the river and at least a mile from the point at 

 widch the trail enters the Elk Creek Meadows. It also occurs in the 

 low clifl's which border the meadows. It may be seen in a curious 

 tiiangular mound, from 1 to 3 feet in height, that lies in the midst of 

 the smooth meadow. On our left, as we pass by the mound, is a low, 

 flat-topped hill (from which the sketch given in Plate XXIIl is taken). 

 Along the base of this there is a dark ledge of the brecciated trachyte 

 that at first sight would be taken for basalt. At the left base of this 

 hill, facing Elk Creek, the garnetiferous schists outcrop. The hill is 

 capped by a mass of grayish rhyolite (No. 4, Captain Button's cata- 

 logue) which is similar to the rhyolite of the plateau. Between this 

 hill and thebridge, a distance of upwards of a mile, the surface is covered 

 mostly with drift, such outcrops as occur being chiefly basalts. In 

 passing over this drift-covered terrace to the north, keeping close to 

 the base of Garnet Hill, we find the reddish brecciated trachyte out- 

 cropping in a ledge that overlooks the Yellowstone, where it turns to 

 tbe north around Garnet Hill. As we i)ass to the right, up the river, 

 however, the trachytes soon give way to basalts and the only rocks from 

 this to the forks are of tl)e latter kind. 



Along the southern side of the valley, midway between the bridge 

 and Elk Creek, and near the low pass in the meadows, where the Elk 

 Creek drainage meets the Lost Creek drainage, there are low bluffs 

 formed of the brecciated trachyte. Here it is chiefly greenish in color, 

 but in other respects is identical with the trachytes elsewhere. There 

 are also basalts in the vicinity, but in what relation to the tracliyte I 

 am unable to say. One small mass of this basalt (No. 20, Captain 

 Button's catalogue) occurs in the lowest part of the low pass just men- 

 tio:e(;l. 



